The inventors of the present invention have proposed various fabrication methods of a self-written optical waveguide. As a self-written optical waveguide, for example, a self-written optical waveguide in which a substantially cylindrical core is formed from an optical fiber end through an upward taper (a core diameter of the self-written optical waveguide gradually increases from the optical fiber end) has been reported in academic conferences and the like.
However, there have been cases in which a core diameter is not constant and upward and downward tapers are repeatedly formed depending on selection of light curing resin or an incident mode in causing the curing light to enter into an optical fiber.
Moreover, regarding a problem that the taper of the core at a desired position of the core cannot be desirably controlled, no new technology has been reported after introduction of following documents.
[Patent Document 1]
Japanese Unexamined Patent Application Publication No. 4-165311
[Patent Document 2]
Japanese Unexamined Patent Application Publication No. 2003-4990